Ultrasound imaging systems are a powerful tool for performing real-time, non-invasive imaging procedures in a wide range of medical applications. In a typical ultrasound system, a transducer sends out ultrasound signals and receives their echoes. The echoes are processed to produce an ultrasound image of the target anatomy.
The quality of the ultrasound image depends on the skill and experience of the operator. An important and challenging part of acquiring high-quality images is adjusting the various imaging parameters.
Ultrasound waves are attenuated as they propagate deeper into the material being imaged. This results in darker pixels as the depth increases. It is desirable that anatomically identical regions be displayed with the same brightness regardless of depth. Depth-dependent gain, or time gain compensation (TGC), is applied to correct images.
Time gain compensation is further complicated by the fact that the amount of attenuation depends on frequency: higher frequencies are attenuated more than lower frequencies.
Conventional ultrasound systems have large control interfaces with numerous controls which allow operators to adjust a wide range of parameters. For example, time-gain compensation is often adjusted by manually adjusting a number of mechanical sliders that each adjust the gain for a particular depth range. Operators typically rely on trial and error to adjust the gains to produce good images.
There is an increasing demand for small portable ultrasound imaging devices that are still capable of acquiring good quality ultrasound images. Increasing portability and simplicity often involves or requires reducing the number of controls to accommodate smaller screens and smaller devices. Fewer controls and reduced need for manual adjustments also make it easier for new ultrasound operators to learn how to use such smaller devices.
There remains a need for methods and apparatus operable to apply automatic time gain compensation in real time, particularly on simple and/or handheld ultrasonic imaging machines.